It is stated multiple times across the article that the probe would need a means of changing is trajectory, but not even a hint of idea how that could possibly be done is given. So the most important and blocking aspect of the mission is simply skimmed over, and the rest of it is built upon this omission as if it was something trivial to come up with.
Does anyone have an idea how to equip a 1g spacecraft with any means to steer itself at 1/3 speed of light? The kinetic energy at that speed would seem to require something very incompatible with the weight constraint, to my understanding.
Since momentum is conserved, why not just have a 2 of the 1 g probes strapped to each other with a spring in between. When you need a course correction at 100 AU out (or whatever). The probes calculate how much of a correction is needed, adjusts a screw that tightens or loosens tension on the spring, reorients itself appropriately with a reaction wheel, then the two probes are released from each other, begin pushed apart with the spring. One probe gets the trajectory correction it needs, and the other gets further off course. Maybe with some gravity assists with nearby objects.
Isn’t that basically how a rocket works? Throw stuff out one side to get the thing on the other side moving. Not sure how this would compare to a rocket engine with hyperbolic fuel.
Because the specific impulse of the spring is negligible when you’re moving at 1/10c and why would they send a 1g probe if they could accelerate 100kg to that speed? Why do you suppose doubling the weight would be free instead of making the system infeasible?
What would the "screw" push off of? That rotational force would need to go somewhere or be corrected, else the probes would just rotate. I guess a gyroscope could do that, but what you're describing just sounds... very roundabout, and in terms of force, a few kilos of propellant would have the same effect.
It's not skimmed over, they cover it near the end in the "Requirements and challenges" section:
> The most challenging phase of the mission may be related to how the nanocraft can transfer from an unbound to a bound orbit and start orbiting around the compact object. All possible solutions should be considered carefully. In the case the transfer is not possible, we may redesign the mission to perform the scientific tests when the nanocraft passes close to the black hole. For example, when the nanocraft is close to the black hole, it may separate into a mother-nanocraft (with a wafer and sail) and a number of small nanocrafts (without sails). The nanocrafts could communicate with each other by exchanging electromagnetic signals. The mother-nanocraft could compare the trajectories of the small nanocrafts to those expected in a Kerr spacetime and send the data to Earth.
Light sales can theoretically be used to not only accelerate away from Earth, but also decelerate at the end of an interstellar journey (see Robert L Forward's work). The practicality of that is another matter.
There’s a really straightforward way to avoid a parabolic trajectory with a black hole. But data retrieval gets a bit difficult.
More seriously, it floors me how often and consistently people forget that the accretion disk is essentially a partial accelerator and crossing or entering it will probably pulverize you to radioactive dust. Possibly before you could hit the event horizon.
> Does anyone have an idea how to equip a 1g spacecraft with any means to steer itself at 1/3 speed of light? The kinetic energy at that speed would seem to require something very incompatible with the weight constraint, to my understanding.
I'm also wondering how such a thing is supposed to communicate back to us over dozens of light years. That also seems incompatible with the weight constraint.
>I'm also wondering how such a thing is supposed to communicate back to us over dozens of light years.
Just spit-balling here. Send out the first batch of probes and then 5 years later send another batch of probes. The first batch of probes does their surveying for 5 years, when the later batch of probes start arriving. The data is uploaded to the late-comers, who aren't on an intercept course. Instead they are on a trajectory that causes them to swing around the black hole, and head on back to earth with the data.
>I'm also wondering how such a thing is supposed to communicate back to us over dozens of light years.
Split particle pairs. We just need to repeal the no cloning theorem, maybe if we promise to not use it for FTL communication the legislators would go for it.
People don't realise this, but you can steer perfectly fine with a solar sail. That's because photons transfer momentum not just when they hit the sail, but also when they are emitted after reflection. So just by turning the sail at an angle, you can create a force in any direction perpendicular to the velocity vector. Using a two sail system, you can even accelerate and slow down along a single beam path. So you could theoretically travel to mars with a constant acceleration/deceleration phase (like a flip-and-burn in the Expanse) using only one beam emitter on earth.
> So the most important and blocking aspect of the mission
Idk, i think the fact they are using statistical arguments that there should be a nearby black hole, but haven't actually found any or have any idea where they are, is pretty blocking.
"steering" is a word that can lead to confusion because it leverages the intuition that we have with our ground vehicles.
A change in direction in space requires accelerating the vehicle in some direction, the effect of which is just simple vector addition of the velocity vector of the vehicle.
So if you are going with a huge velocity in one direction and you want to change direction significantly in another direction you have to change velocity (accelerate) a lot in order for the combined vectors to produce a significantly different final velocity vector
What’s be super cool is discovering a! asteroid mass primordial black hole in our solar system. No epic interstellar flight needed.
It would be super hard to detect though. We’d have to spot it by gravitational effects or get very lucky and notice lensing. It would emit nothing unless it happened to be nomming on some matter, and even then it’d be so small that the signal would be weak.
I read somewhere that a black hole with the mass of the moon will absorb about as much cosmic radiation as it emits Hawking radiation. This is a fine line between "the black hole disappears before we can examine it" and "oops, we got eaten by a black hole".
If it's in a stable orbit in the solar system, it wouldn't be able to "eat" us. Black holes gravitate exactly the same as any other mass, so it would have the same gravitational effect on Earth as any object if the same mass.
What makes black holes special is that you can get much close to their center of mass than you can with normal objects. When you're that close - inside the radius that a normal density object of that mass would have - then you experience gravity at a much higher strength than normal.
Put another way, even if our Moon was a black hole with the same mass, very little would change except that it would no longer reflect sunlight. Ocean tides on Earth would remain the same. You wouldn't want to try to land on it though...
Hey, its not like an analog of "Yeah, lets just throw some more mass at the newly-forming black hole in our neighbourhood", said every human that has ever thrown things into the fire, forever ..
Would it? I would've thought there is enough dust in the solar system that it would create constant xray emissions. Even if it's faint, it would stick out like a sore thumb on super sensitive xray telescopes.
An asteroid-mass black hole is around a micron across. It's not going to be nomming on much because the matter distribution inside the solar system isn't that dense.
Any tiny black hole born in the big bang would either have evaporated (if Hawking was right...) or would have grown much larger by now.
Even a moon-mass black hole (0.1mm) wouldn't be eating much, although its gravitational effects would be much more obvious.
I remember reading somewhere that it's possible for such a black hole to get captured by an asteroid (or vice versa, I guess), and happily live inside a rock, slowly orbiting inside the asteroid, sucking up atoms here and there.
It would be detectable as an asteroid that's twice as dense as it should be.
If it was asteroid mass, wouldn't it have the same gravitational effect of an asteroid itself? Plus, someone else mentioned it'd be like a micron across, which if my pop-sci understanding of these things is correct, it'd disappear in a poof of hawking radiation.
It would have the same mass, and it would be tiny -- like the size of a hydrogen or helium atom.
AFAIK an asteroid mass black hole wouldn't evaporate yet since the CMB is still warmer than its Hawking temperature. Very tiny black holes would have evaporated earlier in the universe. A black hole evaporates when its Hawking temperature exceeds the ambient temperature.
We wouldn't have to get lucky if it was on the last stages of evaporating. If it has reached a mass of about a billion kg it would be shining plenty bright to detect, and would only have a few thousand years to live before destroying most life on Earth with gamma radiation.
How do you stop if your solar sail has you going near light speed? Or does it strand you halfway between stars in the doldrums where the force on both sides of your sail equals out from two stars?
You don't stop this type of craft, it's strictly accelerate and coast type of thing.
Also note that "solar sail" is a bit misleading, the (now apparently dead) Breakthrough Starshot design was a big reflector "sail" in space and very many lasers on Earth to power it, it's not actually driven by a stellar wind directly.
This suggests ejecting a secondary mirror in front of the craft to reflect light to brake the original craft: https://arxiv.org/pdf/1604.01356:
"...or by ejecting a reflector that is then used as a braking system (similar to thrust reversal on jets) but this only works if the payload is still within illumination range of the primary laser system"
Solar sails aren't powered by solar wind but by light reflecting off like the probe. But the probe would be powered by laser so not really "solar" sail. Light sail is the generic term.
I don't think we can just go near speed of light. Even hard vacuum out there contains particles. Heliosphere is chock full of them, then Oort cloud has stuff way bigger than that (or any probe), even if sparsely spread out. Then there is cosmic stuff outside, as Voyager found out.
Getting hit by some random molecule when orbiting Earth or just travelling say 30,000 kmh is one thing. Getting hit by swarms of molecules with say 0.5c can be catastrophic to the material. Now imagine wading through some space dust cloud, or even plasma cloud (ie remnant of some bygone supernova).
Star trek had shields, and for good reasons. Super strong magnetic field may divert some charged particle, but helium molecule is just a helium molecule, no extra charge to play with.
If intelligent life evolved on a planet of a brown dwarf — a “failed” star — that was ejected from its original galaxy deep into intergalactic space, then that species would be spectacularly isolated.
Note that the “naked eye” stars we see in our night sky are all big, bright stars in our immediate vicinity.
Outside of a galaxy the night sky would be black, other than some fuzzy smudges of other galaxies.
It would be a long time before any such species would figure out what galaxies are, what stars are, and their own relationship to those things.
Their study of astronomy would take a wildly different path even assuming they end up at the same conclusions!
And then what? What missions could they envisage, tens of thousands of light years away from the next nearest… anything?
Isn't Relativistic time dilation a problem for this idea? To the probe, the trip is only a few centuries but to us on Earth, millions of years. Maybe 0.1c isn't enough to cause this to be a huge problem but I think it is. Perhaps one of you Einstein enjoyers can tell us for certain.
Time dilation is 1/sqrt(1 - (v/c)^2). So at 0.1c that’s 0.5%. Certainly much higher than any human has ever experienced! But not exactly gonna change 100y to 100,000,000y.
No need to be snarky and especially not here re basic science. Time dilation happens exponentially, ie with 0.5c you don't have time going 1/2 slower, rather a miniscule amount. Once you keep approaching speed of light closer and closer, all things go extreme (time, energy required, mass and so on).
build very large optical interometric telescopes, put the in geosycrenous orbit or L², and point them at various gravitational lenses in the universe till something interesting shows up, like the well lit event horison of a black hole surrounded by bright stars.
given starships load carrying capacity, previos mass restrictions, are gone, with cost guaranteed to be dramaticaly less, and time frames that will get public interest, plus the same instrument can be used to image exoplanets surface's at high resolutions
et say cheese
Readit News
Does anyone have an idea how to equip a 1g spacecraft with any means to steer itself at 1/3 speed of light? The kinetic energy at that speed would seem to require something very incompatible with the weight constraint, to my understanding.
https://en.wikipedia.org/wiki/Gravity_assist
also:
Roundtrip Interstellar Travel Using Laser-Pushed Lightsails
https://ia800108.us.archive.org/view_archive.php?archive=/24...
> The most challenging phase of the mission may be related to how the nanocraft can transfer from an unbound to a bound orbit and start orbiting around the compact object. All possible solutions should be considered carefully. In the case the transfer is not possible, we may redesign the mission to perform the scientific tests when the nanocraft passes close to the black hole. For example, when the nanocraft is close to the black hole, it may separate into a mother-nanocraft (with a wafer and sail) and a number of small nanocrafts (without sails). The nanocrafts could communicate with each other by exchanging electromagnetic signals. The mother-nanocraft could compare the trajectories of the small nanocrafts to those expected in a Kerr spacetime and send the data to Earth.
Light sales can theoretically be used to not only accelerate away from Earth, but also decelerate at the end of an interstellar journey (see Robert L Forward's work). The practicality of that is another matter.
More seriously, it floors me how often and consistently people forget that the accretion disk is essentially a partial accelerator and crossing or entering it will probably pulverize you to radioactive dust. Possibly before you could hit the event horizon.
I was a bit confused by your comment, but I think the article you're referring to is not the OP, but the article the OP was commenting on: https://www.cell.com/iscience/fulltext/S2589-0042(25)01403-8...
> Does anyone have an idea how to equip a 1g spacecraft with any means to steer itself at 1/3 speed of light? The kinetic energy at that speed would seem to require something very incompatible with the weight constraint, to my understanding.
I'm also wondering how such a thing is supposed to communicate back to us over dozens of light years. That also seems incompatible with the weight constraint.
Just spit-balling here. Send out the first batch of probes and then 5 years later send another batch of probes. The first batch of probes does their surveying for 5 years, when the later batch of probes start arriving. The data is uploaded to the late-comers, who aren't on an intercept course. Instead they are on a trajectory that causes them to swing around the black hole, and head on back to earth with the data.
Not like a 1 gram probe is going to be expensive compared to the launch system.
Split particle pairs. We just need to repeal the no cloning theorem, maybe if we promise to not use it for FTL communication the legislators would go for it.
Idk, i think the fact they are using statistical arguments that there should be a nearby black hole, but haven't actually found any or have any idea where they are, is pretty blocking.
A change in direction in space requires accelerating the vehicle in some direction, the effect of which is just simple vector addition of the velocity vector of the vehicle.
So if you are going with a huge velocity in one direction and you want to change direction significantly in another direction you have to change velocity (accelerate) a lot in order for the combined vectors to produce a significantly different final velocity vector
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Won't happen under this administration and really might take a planet-wide effort but it would be incredible
https://www.centauri-dreams.org/2022/07/22/solar-gravitation...
https://www.nasa.gov/general/direct-multipixel-imaging-and-s...
https://www.universetoday.com/articles/a-mission-to-reach-th...
It would be super hard to detect though. We’d have to spot it by gravitational effects or get very lucky and notice lensing. It would emit nothing unless it happened to be nomming on some matter, and even then it’d be so small that the signal would be weak.
I read somewhere that a black hole with the mass of the moon will absorb about as much cosmic radiation as it emits Hawking radiation. This is a fine line between "the black hole disappears before we can examine it" and "oops, we got eaten by a black hole".
What makes black holes special is that you can get much close to their center of mass than you can with normal objects. When you're that close - inside the radius that a normal density object of that mass would have - then you experience gravity at a much higher strength than normal.
Put another way, even if our Moon was a black hole with the same mass, very little would change except that it would no longer reflect sunlight. Ocean tides on Earth would remain the same. You wouldn't want to try to land on it though...
Would it? I would've thought there is enough dust in the solar system that it would create constant xray emissions. Even if it's faint, it would stick out like a sore thumb on super sensitive xray telescopes.
Any tiny black hole born in the big bang would either have evaporated (if Hawking was right...) or would have grown much larger by now.
Even a moon-mass black hole (0.1mm) wouldn't be eating much, although its gravitational effects would be much more obvious.
It would be detectable as an asteroid that's twice as dense as it should be.
AFAIK an asteroid mass black hole wouldn't evaporate yet since the CMB is still warmer than its Hawking temperature. Very tiny black holes would have evaporated earlier in the universe. A black hole evaporates when its Hawking temperature exceeds the ambient temperature.
Also note that "solar sail" is a bit misleading, the (now apparently dead) Breakthrough Starshot design was a big reflector "sail" in space and very many lasers on Earth to power it, it's not actually driven by a stellar wind directly.
"...or by ejecting a reflector that is then used as a braking system (similar to thrust reversal on jets) but this only works if the payload is still within illumination range of the primary laser system"
Getting hit by some random molecule when orbiting Earth or just travelling say 30,000 kmh is one thing. Getting hit by swarms of molecules with say 0.5c can be catastrophic to the material. Now imagine wading through some space dust cloud, or even plasma cloud (ie remnant of some bygone supernova).
Star trek had shields, and for good reasons. Super strong magnetic field may divert some charged particle, but helium molecule is just a helium molecule, no extra charge to play with.
This is actually I "love" to think about:
What would it be like, to be "stranded" in the space far from any stars?
or in the "voids" where there are relatively very few stars/galaxies to begin with?
There must be things drifting there right now...
It would also be the perfect place to HIDE something :)
Note that the “naked eye” stars we see in our night sky are all big, bright stars in our immediate vicinity.
Outside of a galaxy the night sky would be black, other than some fuzzy smudges of other galaxies.
It would be a long time before any such species would figure out what galaxies are, what stars are, and their own relationship to those things.
Their study of astronomy would take a wildly different path even assuming they end up at the same conclusions!
And then what? What missions could they envisage, tens of thousands of light years away from the next nearest… anything?
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